Direct electrochemical formation of carbonaceous material from CO2 in LiCl-KCl melt

Abstract

The electrochemical reduction of CO2 on a Ni electrode in LiCl-KCl melt at 723 K was studied. The Ni electrode which was partially immersed in the melt was used for electrochemical measurement in order to investigate the relationship between electrical wettability and electrodeposition behavior of carbon from CO2 at the three-phase interface of the Ni electrode/LiCl-KCl melt/CO2 gas. It was found that solid carbon was obtained in the wetted area of the Ni electrode by potentiostatic electrolysis. Under high polarization, a super meniscus was formed at the three-phase interface where the direct electrochemical reduction of CO2 to solid carbon progressed. In addition, SEM and TEM observations with EDS analyses showed that electrodeposited carbon was multi-walled carbon nanotubes with a diameter of 30–50 nm. The dependence of applied potential and electrolytic time on morphology and crystallinity of electrodeposited carbon was also investigated. Based on the experimental results, we have proposed the model of the formation mechanism of the multi-walled carbon nanotube on the Ni electrode. The reported data indicate that carbonaceous materials from CO2 can be obtained by electrochemical technique in molten salt and suggest that the technique contributes to developing the carbon recycling system against global warming.